2008. The year of Reddit's "Cambrian Explosion," as Olson puts it. Why? This was the first point Reddit allowed users to create their own subreddits. Image: Randy Olson

2009. The subredditification continues. Olson's not sure what caused the /r/reddit.com spike in the middle of the year. Image: Randy Olson

2010. Olson calls this "the year gamers and porn invaded," partially thanks to an influx of users from the then-recently-defunct Digg.com Image: Randy Olson

2011. The year of the memes. Also the year mods pulled the plug on the catchall subreddit r/reddit.com. Image: Randy Olson

2012. The Reddit of today, dominated by images and other more mainstream, accessible content. Image: Randy Olson

Recently, we were treated to a clever interactive map of the popular news site reddit, created by Michigan State University PhD student Randy Olson. Instead of one big group of horny programmers, Olson's map revealed a vast constellation of communities dedicated to all sorts of different topics. With these graphs, Olson shows how reddit developed into that diverse ecosystem. The keystone species? Sure enough: Horny programmers!

The most revealing image from Olson's research is this stacked area image of the site’s 24 most popular subreddits over the years. It gives us a stratigraphic look at reddit’s past. Olson calls it the evolution of reddit. You could also say it shows the site's gentrification. Layer by layer, we see the influx of safe, accessible content that has allowed reddit to expand to its massive size today.

Still, the graph shows the site's beginnings in the primordial muck of porn and programming. The r/NSFW subreddit was one of the first, Olson explains (though he notes that the site was never 100 percent NSFW; his graph leaves out /r/reddit.com for purposes of legibility.)

A stacked area graph showing the evolution of Reddit.

Image: Randy Olson

The biggest change came around 2008, the year reddit gave users the ability to create subreddits. This introduction led to reddit’s “Cambrian Explosion,” as Olson puts it. The year starts with an uptick in politics, coincident with the run-up to the 2008 presidential election. Around that same time, you see the supernova of activity that gave us the reddit we know today: subreddits “WTF,” “funny,” “Ask reddit,” and more.

These days, Olson points out, four of the five top subreddits are dedicated to sharing images. “From this brief survey, it becomes abundantly clear that the primary content of reddit nowadays is pictures and videos,” he writes on the project page. “This trend makes sense, too: Pictures are easy content to produce and take only a few seconds to look at, enjoy, and upvote.”

In other words, reddit’s media diet has transformed along with the rest of the internet’s. Even amongst the site’s one-step-ahead-of-the-mainstream audience, quick hits, funny pictures, and cute cat videos rule the day.